Pentesting

Privilege Escalation Abusing Tokens

Tokens

If you don't know what are Windows Access Tokens read this page before continuing:

Maybe you could be able to escalate privileges abusing the tokens you already have

SeImpersonatePrivilege (3.1.1)

Any process holding this privilege can impersonate (but not create) any token for which it is able to gethandle. You can get a privileged token from a Windows service (DCOM) making it perform an NTLM authentication against the exploit, then execute a process as SYSTEM. Exploit it with juicy-potato, RogueWinRM (needs winrm disabled), SweetPotato, PrintSpoofer.

SeAssignPrimaryPrivilege (3.1.2)

It is very similar to SeImpersonatePrivilege, it will use the same method to get a privileged token. Then, this privilege allows to assign a primary token to a new/suspended process. With the privileged impersonation token you can derivate a primary token (DuplicateTokenEx). With the token, you can create a new process with 'CreateProcessAsUser' or create a process suspended and set the token (in general, you cannot modify the primary token of a running process).

SeTcbPrivilege (3.1.3)

If you have enabled this token you can use KERB_S4U_LOGON to get an impersonation token for any other user without knowing the credentials, add an arbitrary group (admins) to the token, set the integrity level of the token to "medium", and assign this token to the current thread (SetThreadToken).

SeBackupPrivilege (3.1.4)

This privilege causes the system to grant all read access control to any file (only read). Use it to read the password hashes of local Administrator accounts from the registry and then use "psexec" or "wmicexec" with the hash (PTH). This attack won't work if the Local Administrator is disabled, or if it is configured that a Local Admin isn't admin if he is connected remotely. You can abuse this privilege with: https://github.com/Hackplayers/PsCabesha-tools/blob/master/Privesc/Acl-FullControl.ps1 or with https://github.com/giuliano108/SeBackupPrivilege/tree/master/SeBackupPrivilegeCmdLets/bin/Debug or following IppSec in https://www.youtube.com/watch?v=IfCysW0Od8w&t=2610&ab_channel=IppSec

SeRestorePrivilege (3.1.5)

Write access control to any file on the system, regardless of the files ACL. You can modify services, DLL Hijacking, set debugger (Image File Execution Options)… A lot of options to escalate.

SeCreateTokenPrivilege (3.1.6)

This token can be used as EoP method only if the user can impersonate tokens (even without SeImpersonatePrivilege). In a possible scenario, a user can impersonate the token if it is for the same user and the integrity level is less or equal to the current process integrity level. In this case, the user could create an impersonation token and add to it a privileged group SID.

SeLoadDriverPrivilege (3.1.7)

Load and unload device drivers. You need to create an entry in the registry with values for ImagePath and Type. As you don't have access to write to HKLM, you have to use HKCU. But HKCU doesn't mean anything for the kernel, the way to guide the kernel here and use the expected path for a driver config is to use the path: "\Registry\User\S-1-5-21-582075628-3447520101-2530640108-1003\System\CurrentControlSet\Services\DriverName" (the ID is the RID of the current user). So, you have to create all that path inside HKCU and set the ImagePath (path to the binary that is going to be executed) and Type (SERVICE_KERNEL_DRIVER 0x00000001). Learn how to exploit it here.

SeTakeOwnershipPrivilege (3.1.8)

This privilege is very similar to SeRestorePrivilege. It allows a process to “take ownership of an object without being granted discretionary access” by granting the WRITE_OWNER access right. First, you have to take ownership of the registry key that you are going to write on and modify the DACL so you can write on it.

SeDebugPrivilege (3.1.9)

It allows the holder to debug another process, this includes reading and writing to that process' memory. There are a lot of various memory injection strategies that can be used with this privilege that evade a majority of AV/HIPS solutions.

Check privileges

whoami /priv

The tokens that appear as Disabled can be enable, you you actually can abuse Enabled and Disabled tokens.

Table

Full token privileges cheatsheet at https://github.com/gtworek/Priv2Admin, summary below will only list direct ways to exploit the privilege to obtain an admin session or read sensitive files.

Privilege

Impact

Tool

Execution path

Remarks

SeAssignPrimaryToken

Admin

3rd party tool

"It would allow a user to impersonate tokens and privesc to nt system using tools such as potato.exe, rottenpotato.exe and juicypotato.exe"

Thank you Aurélien Chalot for the update. I will try to re-phrase it to something more recipe-like soon.

SeBackup

Threat

Built-in commands

Read sensitve files with robocopy /b

- May be more interesting if you can read %WINDIR%\MEMORY.DMP - SeBackupPrivilege (and robocopy) is not helpful when it comes to open files. - Robocopy requires both SeBackup and SeRestore to work with /b parameter.

SeCreateToken

Admin

3rd party tool

Create arbitrary token including local admin rights with NtCreateToken.

SeDebug

Admin

PowerShell

Duplicate the lsass.exe token.

Script to be found at FuzzySecurity

SeLoadDriver

Admin

3rd party tool

1. Load buggy kernel driver such as szkg64.sys 2. Exploit the driver vulnerability Alternatively, the privilege may be used to unload security-related drivers with ftlMC builtin command. i.e.: fltMC sysmondrv

1. The szkg64 vulnerability is listed as CVE-2018-15732 2. The szkg64 exploit code was created by Parvez Anwar

SeRestore

Admin

PowerShell

1. Launch PowerShell/ISE with the SeRestore privilege present. 2. Enable the privilege with Enable-SeRestorePrivilege). 3. Rename utilman.exe to utilman.old 4. Rename cmd.exe to utilman.exe 5. Lock the console and press Win+U

Attack may be detected by some AV software.

Alternative method relies on replacing service binaries stored in "Program Files" using the same privilege

SeTakeOwnership

Admin

Built-in commands

1. takeown.exe /f "%windir%\system32" 2. icalcs.exe "%windir%\system32" /grant "%username%":F 3. Rename cmd.exe to utilman.exe 4. Lock the console and press Win+U

Attack may be detected by some AV software.

Alternative method relies on replacing service binaries stored in "Program Files" using the same privilege.

SeTcb

Admin

3rd party tool

Manipulate tokens to have local admin rights included. May require SeImpersonate.

To be verified.

Reference